The present invention relates to an electron beam exposure apparatus.
The electron beam exposure apparatus is used to expose a given pattern on the photoresist of the wafer in the manufacturing process of semiconductor integrated circuit device. The electron beam exposure apparatus is superior to the ultraviolet exposure apparatus when it is intended to integrate in high density semiconductor devices. In the ultraviolet exposure apparatus, the diffraction of ultraviolet restricts the resolution limit so that the minimum width of the exposure pattern is at most 2.mu.. Further narrower width thereof is almost impossible. To the contrary, in the case of the electron beam exposure apparatus, the minimum width of the exposure pattern is about 0.1.mu. for the reason that the wave length of the electron beam is very short as compared to that of the ultraviolet and thus the affect of diffraction is small, thereby enabling a very small resolution limit.
Generally, the electron beam exposure apparatus is classified into electron beam scanning type exposure apparatus and electron beam projection type exposure apparatus. The electron beam scanning type exposure apparatus is such that a single electron beam is used to scan the photoresist on the wafer and projection and non-projection are repeated every scanning unit in accordance with the exposure pattern. The electron beam projection type exposure apparatus uses a foil mask of the so called self-supporting type consisting of a plurality of masks permitting electron beams configured in a predetermined pattern to pass therethrough. The parallel electron beams are irradiated onto the foil mask to form an image on the photoresist of the wafer. Both the exposure apparatuses of the electron beam scanning type and the electron beam projection type are suitable for the high density integration of semiconductor devices, as compared to the ultraviolet exposure apparatus. However, these apparatuses suffer from some disadvantages and present problems in practical use.
As mentioned above, a single electron beam scans the wafer in the electron beam scanning apparatus. For this, various types of patterns may be easily and precisely exposed. But this type exposure apparatus takes a relatively long time for one time pattern exposure. In the manufacturing process of semiconductor devices, several time exposures of the pattern are necessary. Therefore, the electron beam scanning exposure apparatus is improper in application for the mass production of the semiconductor integrated circuit devices.
On the other hand, the electron beam projection type exposure apparatus takes a very short time, for example, several seconds, for one time exposure of the pattern and has a very deep focal depth. With the deep focal depth, the pattern may be exposed precisely even if the wafer is deformed or the moving stage vertically moves a slight degree. However, it is very difficult to make precisely the foil mask. More adversely, such a precise foil mask must be made separately for individual circuit constructions of semiconductor devices. Thus, the electron beam projection type exposure apparatus is defective in this regard.